1. Field of Invention
The invention relates to a hinge for a pet door. More specifically, this invention relates to a flexible hinge adapted to resist damage or breakage resulting from undesirable forces applied to the hinge during the normal course of operation.
2. Description of the Related Art
Conventional pet doors have a movable flap residing within a frame. Soft flap pet doors take advantage of the flexibility of the flap to allow ingress and egress, such as that shown and described by Davlantes in U.S. Pat. No. 4,408,416. Hard flap pet doors must use a hinge mechanism to allow for movement of the flap. There are many basic hinge mechanisms commonly employed. One example of a common hinge mechanism is the molding of the shaft and the hinge tube as part of the flap and the frame, such as that shown and described by Green, in U.S. Pat. No. 4,776,133. Another example, is the use of a cam resting on a shelf, such as that shown and described in by Marsh, et al., in U.S. Pat. No. 6,385,909, or a cam resisted by a biasing member such as that shown and described by Pennock in U.S. Pat. No. 3,978,616. In yet another example, the flap and the frame may be connected by conventional hinges, such as that shown and described by Peterson in U.S. Pat. No. 5,581,940.
Each of the hard flap pet doors share the common concern of the hinge mechanism being subjected to potentially damaging forces, for example, the over-rotation of the flap. If the flap is pushed beyond the rotational limits afforded by the hinge mechanism, some portion of the rigid structure is forced to give. This can result in the breakage of the flap or the frame and/or the destruction of the hinge mechanism including but not limited the breakage of the shafts or the hinge tubes, the separation of the hinge from the flap or the frame, the breakage of the cam member, or merely the deformation of the hinge mechanism outside of tolerances resulting in unreliable performance. The same potential for damage often results from the physical construction of the pet door. When the hard flap rotates until it is contact with the top of the frame member, the pivot point is moved from the hinge mechanism to the point of contact between the frame and the flap. This results in lateral (i.e., non-rotational) forces, which a conventional hinge is not designed to accommodate, being applied to the hinge.